Integrated process for carbon capture and energy production

ABSTRACT

The present invention pertains to new methods for generating energy and useful nitrogen compounds from captured carbon dioxide. It involves employing an osmotic engine, draw solution, and feed solution. An osmotic gradient between the solutions assists in generating energy and a solution of ammonium carbonate, ammonium bicarbonate or mixture thereof. This solution may be decomposed to form ammonia, carbon dioxide, a precipitate, or a mixture thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application62/090,272 filed Dec. 10, 2014; U.S. provisional patent application62/106,822 filed Jan. 23, 2015; and U.S. provisional patent application62/159,481, filed May 11, 2015, each of which is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The inventions relate to methods and systems to generate electricityand/or useful compounds from captured carbon dioxide.

BACKGROUND AND SUMMARY OF THE INVENTION

Climate change due to increasing amounts of greenhouse gases in Earth'satmosphere poses one of the greatest threats to mankind and world'secosystems as a whole. Carbon dioxide (CO₂) is one of the mostsignificant contributors to climate change, making up approximately 77%of the world's greenhouse gas emissions by some estimates. Many of theCO₂ emissions are due to, for example, combustion from power plants orother industrial facilities.

There have been numerous methods and systems developed in attempts toreduce and/or eliminate these emissions. Such methods include carboncapture and storage or sequestration. Such methods often rely onseparating (i.e. capturing) CO₂ from, for example, combustion gas orother CO₂ sources. Unfortunately, in order to be effective the capturedCO₂ must then be disposed as opposed to released to the environment. Thedisposal methods developed thus far are very inadequate. For example,one such disposal method employed is compression followed by, forexample, delivery to an underground geological formation or other mannerof containment. In another method carbon dioxide is captured by ammoniaand used in a forward osmosis process with high temperature andpressure. Unfortunately, such current methods often require complexapparatuses, are expensive to implement, consume vast amounts of energy,and/or usually do not yield usable or saleable products.

It would therefore be desirable to determine new methods for reducingand/or eliminating CO₂ emissions. It would further be advantageous ifsuch new methods could be implemented using less complex equipment, werecost-effective, consumed less energy, and/or yielded usable or saleableproducts. Advantageously, the instant processes accomplish one or moreup to all of the aforementioned.

In one embodiment the invention pertains to an integrated process forgenerating energy and useful nitrogen compounds from captured carbondioxide. The process comprises forming a solution of ammonium carbonate,ammonium bicarbonate, ammonium carbamate or mixture thereof. Thesolution is formed from at least a portion of captured carbon dioxide.The solution of ammonium carbonate, ammonium bicarbonate, ammoniumcarbamate or mixture thereof is decomposed to form ammonia, carbondioxide, a precipitate, or a mixture thereof. The decomposing of thesolution is further characterized by one or more of the following:

(a) decomposing such that ammonia and carbon dioxide are formed in amolar ratio suitable for production of ammonium carbamate, urea, or aderivative thereof;

(b) decomposing at about atmospheric pressure;

(c) decomposing in the substantial absence of high temperatureequilibrium;

(d) decomposing using low grade heat;

(e) decomposing in the presence of a semipermeable membrane, condensing,or a water soluble, solvent under suitable conditions to formsubstantially separated ammonia and carbon dioxide; or

(f) decomposing under conditions to form a precipitate comprising a saltof carbonate, bicarbonate, carbamate, or a mixture thereof.

In another embodiment the integrated process may comprise employing anosmotic engine. The osmotic engine comprises: (1) the formed solution ofammonium carbonate, ammonium bicarbonate, ammonium carbamate or mixturethereof as a draw solution and (2) a feed solution having a lowerosmotic pressure than said draw solution to generate a gradient. Thegradient may be used to generate energy and a second solution ofammonium carbonate, ammonium bicarbonate, ammonium carbamate or mixturethereof wherein said second solution has a lower osmotic pressure thanthe draw solution and wherein at least a portion of said second solutionis subjected to decomposing as described above.

In another embodiment the invention pertains to an integrated processfor generating energy and useful nitrogen compounds from captured carbondioxide comprising capturing carbon dioxide from a combustion emissionstream by exposing the carbon dioxide to aqueous ammonia underconditions suitable to form a draw solution comprising ammoniumcarbonate, ammonium bicarbonate, ammonium carbamate, or mixture thereof.An osmotic engine is employed comprising: (1) the draw solution and (2)a feed solution having a lower osmotic pressure than said draw solutionto generate a gradient. The gradient is used to generate energy and asecond solution of ammonium carbonate, ammonium bicarbonate, ammoniumcarbamate, or mixture thereof wherein said second solution has a lowerosmotic pressure than the draw solution. The second solution of ammoniumcarbonate, ammonium bicarbonate or mixture thereof may be decomposed toform ammonia, carbon dioxide, or a mixture thereof. The decomposing ofthe second solution is further characterized by one or more of thefollowing:

(a) decomposing such that ammonia and carbon dioxide are formed in amolar ratio suitable for production of ammonium carbamate, urea, or aderivative thereof;

(b) decomposing at about atmospheric pressure;

(c) decomposing in the substantial absence of high temperatureequilibrium;

(d) decomposing using low grade heat; or

(e) decomposing in the presence of a semipermeable membrane, cooling, ora water soluble solvent under suitable conditions to form substantiallyseparated ammonia and carbon dioxide. The ammonia and carbon dioxidethat were decomposed from the second solution may be reacted underconditions to form one or more useful products selected from the groupconsisting of ammonium carbamate, urea, or a derivative thereof.

In another embodiment the invention pertains to an integrated processfor generating energy and useful nitrogen compounds from captured carbondioxide comprising contacting ammonia, carbon dioxide or a solution madetherefrom with a suitable draw solution. The contacting is conductedunder conditions such that a precipitate is formed which comprisesammonia carbonate, ammonia bicarbonate, ammonia carbamate, or a mixturethereof. Suitable draw solutions may be selected from the groupconsisting of ammonium sulfate, ammonium nitrate, potassium carbonate,potassium bicarbonate, or a mixture thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of Pressure Retarded Osmosis Waste HeatRecovery System with Carbon Capture using Pressurization andDepressurization.

FIG. 2 illustrates an embodiment of Forward Osmosis Waste Heat RecoverySystem with Carbon Capture using Pressurization and Depressurization.

FIG. 3 illustrates an embodiment of Pressure Retarded Osmosis Waste HeatRecovery System with Carbon Sequestration through the Production ofUrea.

FIG. 4 illustrates an embodiment of Forward Osmosis Waste Heat RecoverySystem with Carbon Sequestration through the Production of Urea.

FIG. 5 illustrates an embodiment of Higher Efficiency Pressure RetardedOsmosis Waste Heat Recovery System through Addition of Water SolubleOrganic Solvent to Precipitate Ammonium Bicarbonate Solid from AqueousSolution.

FIG. 6 illustrates an embodiment of Higher Efficiency Forward OsmosisHigh Concentration Water Desalination and Waste Heat Recovery Systemthrough Addition of Organic Solvent to Precipitate Ammonium BicarbonateSolid from Aqueous Solution.

FIG. 7 illustrates an embodiment of Pressure Retarded Osmosis Waste HeatRecovery and Carbon Capture System through Addition of Water SolubleOrganic Solvent to Decompose Ammonium Bicarbonate.

FIG. 8 illustrates an embodiment of Membrane Carbon Capture.

FIG. 9 illustrates an embodiment of Urea Production.

FIG. 10 illustrates an embodiment of Urea Production Using Common IonPrecipitation.

FIG. 11 illustrates an embodiment of Basic Production Process withCopper Battery and Pressure Retarded Osmosis Membrane Prior to HeatExchanger.

FIG. 12 illustrates an embodiment of Basic Production Process withCopper Battery.

FIG. 13 illustrates an embodiment of Basic Production Process withCopper Battery and Pressure Retarded Osmosis Membrane After HeatExchanger.

FIG. 14 illustrates the dependence of ammonia/ammonium ion ratio as afunction of pH.

DETAILED DESCRIPTION

The instant invention generally pertains to an integrated process forgenerating energy and useful nitrogen compounds from captured carbondioxide. The source of the captured carbon dioxide is not particularlyimportant and generally it may be from any useful source. Such sourcesinclude, but are not limited to, combustion or oxidation of one or morehydrocarbons, from steam reforming, from gas shift reaction, fromcatalytic reforming, from natural gas purification, from land fill gas,from biogas, from waste water treatment, fermentation, respiration, fromair, or from mixtures thereof. Carbon dioxide from gas purification istypically from gas streams containing hydrogen, methane, or otherdesired gas by capturing carbon dioxide in these gas streams at atemperature of from about 50 to about 70° C.

Similarly, the method of capturing the carbon dioxide is not criticaland may, of course, vary depending upon the source of the carbondioxide, equipment available, desired purity, etc. In one embodimentcarbon dioxide may be captured from the combustion or oxidation of oneor more hydrocarbons in some convenient manner. For example, flue gasfrom a power plant of some sort may be subjected to, for example,ammonia, preferably aqueous ammonia, or other suitable substance suchthat the carbon dioxide is dissolved and therefore removed from the fluegas. In such a method it is not particularly critical when the carbondioxide is captured so long as it is not released to the environment.Moreover, the flue gas may be further treated before or after beingsubjected to the aqueous ammonia depending upon the amounts andcomponents of the starting flue gas and desired treated product.

The capturing of the carbon dioxide may be part of or separate from theinstant integrated process. That is, carbon dioxide in flue gas oranother source may be exposed to ammonia to form an aqueous solution ofammonium carbonate, ammonium carbamate, ammonium bicarbonate or mixturethereof for direct use in and as part of the present processes.Generally, when water, carbon dioxide, and ammonia are reacted anaqueous mixture of ammonium carbonate, ammonium bicarbonate, ammoniumcarbamate is formed. The amounts of each component depend on therelative amounts of starting ingredients and the other conditions butgenerally ammonium carbamate is often present in smaller amounts thanammonium carbonate or ammonium bicarbonate.

Carbon dioxide capturing has been described by, for example, thefollowing publications which are incorporated by reference herein: KozakF, Petig A, Morris E, Rhudy R, Thimsen D. Chilled Ammonia Process forCO₂ Capture, Energy Procedia 1 (2009): 1419-1426; Sherrick B, Hammond M,Spitznogle G, Muraskin D., Black S., and Cage M. CCS with Alstom'sChilled Ammonia Process at AEP's Mountaineer Plant.; Yeh, A. “Comparisonof Ammonia and Monoethanolamine Solvents to Reduce CO₂ Greenhouse GasEmissions,” The Science of the Total Environment 228 2-3 (1999): 121-33;and Yeh, James T., Henry W. Pennline, Kevin P. Resnik, and Kathy Rygle.“Absorption and Regeneration Studies for CO₂ .” Proceedings of ThirdAnnual Conference on Carbon Capture & Sequestration, Alexandria, Va.U.S. DOE-NETL and Parson Project Services, Inc., 6 Jun. 2004. Web. 13Nov. 2010.

In another embodiment, captured carbon dioxide may be used to form aprecipitate comprising ammonia carbonate, ammonia bicarbonate, ammoniacarbamate, or a mixture thereof. The precipitate can then be used toform a draw solution for the osmotic engines described below. Theprecipitate may be formed in any convenient manner.

In one embodiment ammonia and carbon dioxide are contacted with asuitable draw solution under conditions such that a precipitate isformed. Alternatively, an aqueous solution made from ammonia and carbondioxide may be contacted with the suitable draw solution underconditions such that a precipitate is formed. In either case the carbondioxide can be from any source including flue gas and other sourcespreviously mentioned. Advantageously, the resulting precipitategenerally comprises ammonia carbonate, ammonia bicarbonate, ammoniacarbamate, or a mixture thereof. In this manner it may be mixed withappropriate aqueous solutions and used as a draw solution in the osmoticengines described below.

Suitable draw solutions for contacting with the ammonia and carbondioxide (or a solution made therefrom) to form a precipitate will varydepending upon the application. Generally it may often be useful toemploy a draw solution with a common ion as the desired precipitate(e.g., ammonium, carbonate, bicarbonate, carbamate). In this manner thepresence of the common ion salt with a more soluble common ion willcause the lower solubility compound, e.g., ammonium bicarbonate, toprecipitate. Such suitable draw solutions thus include, for example,ammonium sulfate, ammonium nitrate, potassium carbonate, potassiumbicarbonate, or a mixture thereof. If desired, the precipitate may befiltered before using it further.

As an alternative to capturing as part of the instant process, anaqueous solution or precipitate of ammonium carbonate, ammoniumbicarbonate or mixture thereof made from captured carbon dioxide may beacquired in any convenient manner for use in the present process. In anyevent, the purity and amounts of carbon dioxide, ammonia, and otheringredients employed is not particularly important so long as a suitableaqueous solution or precipitate of ammonium carbonate, ammoniumbicarbonate or mixture thereof is formed. In some cases it may bedesirable to subject the aqueous solution of ammonium carbonate,ammonium bicarbonate, ammonium carbamate or mixture thereof to furtherpurification or treatment in order to make it suitable as a drawsolution. For example, further amounts of carbon dioxide or ammonia maybe added to make a desired concentration.

Osmotic Engine

The instant process may involve employing an osmotic engine or system.An osmotic engine as used herein is any system wherein an osmoticgradient between one or more draw solutions and one or more feedsolutions may be employed to generate energy, one or more usefulsolutions or precipitates, or some combination thereof. An osmoticgradient may be generated in any convenient manner. For example,differences in salt concentrations may commonly result in useful osmoticgradients.

Specific useful types of osmotic engine systems and other systems thatgenerate electricity from osmotic or concentration gradients mayinclude, for example, pressure retarded osmosis, reverseelectrodialysis, capacitive mixing power production using componentsincluding nano battery electrodes, ultra capacitors, or combinationsthereof. Among other useful references such systems are described in,for example, Energy Procedia, Volume 20, 2012, Pages 108-115 Technoport2012—Sharing Possibilities and 2nd Renewable Energy Research Conference(RERC2012) CAPMIX—Deploying Capacitors for Salt Gradient PowerExtraction; M. F. M. Bijmans, et al. which is incorporated herein byreference. Osmotic heat engines are capable of generating electricityfrom low grade heat, which can be from various waste heat sources (e.g.power plant) or renewable sources, for example, solar photovoltaic wasteheat, solar thermal or geothermal energy.

The osmotic engine system may be an open or closed system and may be acontinuous or batch process depending upon the starting materials,desired products, and equipment. If employing a closed system, then itmay be desirable to have one or more valves or other gas releasemechanisms. In this manner headspace gas such as, for example, carbondioxide may be released while the system is kept at a desired pressure.In some cases it may be desirable to actively pressurize the system suchthat ammonia stays in aqueous solution while carbon dioxide is in theoverhead space. In such a case one or more gas turbines may be used tokeep the system pressurized and, if desired, generate electricity fromthe expansion of carbon dioxide gas. The system can be pressurized inany convenient manner. In one embodiment, carbon dioxide formed in theintegrated process, e.g., from the decomposition of ammonium carbonate,ammonium bicarbonate, ammonium carbamate solution, may be used topressurize the system. Additionally or alternatively, one or more otherpumps or other devices may be employed.

While the above specifically described osmotic engines may be usefullyemployed, the invention will be further described by reference to ageneral osmotic engine system. The system can run carbon capture,electricity generation, and other related processes simultaneously,although different aspects of the system may be conducted at differenttime or rates.

General Osmotic Engine System

In this embodiment, water is transferred from the feed solution acrossone or more membranes. This transfer may be employed, if desired, togenerate useful energy such as electricity. While the energy may begenerated in any convenient manner, a hydroelectric generator may beparticularly useful. Regardless of whether a hydroelectric generator isemployed one or more draw solutions are employed. The draw solutionusually comprises ammonium carbonate, ammonium carbamate, ammoniumbicarbonate or mixture thereof formed from at least a portion ofcaptured carbon dioxide as described above.

Pressure retarded osmosis systems usually separate one or more drawsolutions from one or more feed solutions using one or more membranes.The system may be open to the atmosphere, closed, or partially closeddepending upon the specific equipment, solutions, and membrane employedas well as, the desired results. The draw and feed solution(s) usuallyhave an osmotic pressure differential, i.e., gradient, such that feedsolution from a feed solution chamber is drawn into the draw solution ina draw solution chamber through the one or more membranes. In thismanner, useful kinetic energy may be generated. Such energy may be usedto, for example, spin a turbine or in some other useful manner. Theamount of energy generated is, of course, related to the size ofequipment and amount of solutions. However, generally the amount may beproportional to the differences in osmotic pressure between the draw andfeed solutions.

The type of membrane employed is not particularly critical so long as itfunctions to allow the passage of certain substances, e.g., water, whilepreventing the passage of others, e.g., salts. Such semipermeablemembranes are known in the art and include, for example, a thin-filmcomposite (TFC) membrane. Such membranes may be made of any convenientsubstance. In one embodiment the membrane is comprised of a selectivepolyamide layer with a support such as polysulfone. Suitable membranesare described in, for example, Yip et al., Environ. Sci. Technol., 2011,45 (10), pp 4360-4369 which is incorporated herein by reference.

In one example, if a draw solution comprising ammonium carbonate,ammonium bicarbonate, ammonium carbamate or mixture thereof and one ormore appropriate membranes (pressure retarded or otherwise) are employedwith a feed solution of lower osmotic pressure, then typically usefulenergy is generated.

The feed solution may be any useful solution so long as it has asuitably lower osmotic pressure such that under appropriate conditionsit is capable of migrating across the membrane to the draw solution. Thedegree of osmotic pressure differential or gradient may vary dependingupon the equipment, membrane, solutions, and desired results. Generally,for many systems a gradient may be generated using at least about 2M, orat least about 3M, or at least about 4M draw solution with, for example,a regenerated deionized feed solution. Useful systems may also use afeed solution comprising dissolved substances in such cases forwardosmosis membranes may be employed and the osmotic pressure of the drawsolution should greatly exceed the osmotic pressure of the feedsolution. Accordingly, useful feed solutions include aqueous solutionssuch as deionized water or salt solutions such as, for example,seawater. In some cases at least a portion of the feed solution employedmay be selected from the group consisting of seawater, produced water,or wastewater.

In addition to forming kinetic energy due to the gradient, a secondsolution is usually formed in the draw solution chamber. The secondsolution, like the draw solution, comprises ammonium carbonate, ammoniumbicarbonate, ammonium carbamate or mixture thereof. However, this secondsolution differs from the original draw solution in that it usually hasa lower osmotic pressure than the original draw solution. This isgenerally due to water being drawn across the membrane until the osmoticpressures are substantially equal in the draw solution and feed solutionchambers due to the changes in salt concentrations. Therefore, in mostinstances the remainder of the feed solution will comprise a higherosmotic pressure than the starting feed solution due to the migration ofthe water to the draw solution chamber.

Decomposition of the Solution

Typically, the second solution of ammonium carbonate, ammoniumbicarbonate, ammonium carbamate, or mixture thereof is decomposed toform ammonia, carbon dioxide, a precipitate, or a mixture thereof. Thespecific manner of decomposition will vary depending upon theconcentrations, other ingredients, and desired products and form, e.g.,solution or gas. That is, advantageously decomposition of the secondsolution may be tailored depending upon whether it is desired toseparate ammonia and carbon dioxide, as well as whether gaseous oraqueous substances are desired. If a gaseous mixture of ammonia andcarbon dioxide is formed and separation is desired then a gas separationmembrane or fractional distillation may be subsequently employed.

Advantageously the decomposition may be conducted under relativelymoderate conditions that do not employ large amounts of energy.Moreover, the decomposition may be conducted such that desirable molarratios of carbon dioxide to ammonia are obtained. Such molar ratios maybe very suitable for making urea, ammonium carbamate and other usefulproducts.

Typically, the decomposing of the second concentrated solution ischaracterized by one, or two, or three, or four, or five, or more of thefollowing: (a) decomposing such that ammonia and carbon dioxide areformed in a molar ratio suitable for production of ammonium carbamate,urea, or a derivative thereof; (b) decomposing at about atmosphericpressure; (c) decomposing in the substantial absence of high temperatureequilibrium; (d) decomposing using low grade heat; (e) decomposing inthe presence of a semipermeable membrane, cooling, or a water solublesolvent under suitable conditions to form substantially separatedammonia and carbon dioxide; or (f) decomposing under conditions to forma precipitate comprising a salt of carbonate, bicarbonate, or a mixturethereof.

In one embodiment the decomposing of the second solution ischaracterized by decomposing such that ammonia and carbon dioxide areformed in a molar ratio such that subsequent processing may produce asuitable useful or saleable product. Such useful or saleable productsinclude, for example, hydrocarbons as well as, compounds containingnitrogen such as ammonium carbamate, urea, or a derivative thereof suchas cyanuric acid. In one embodiment the molar ratio may be controlledsuch that the molar ratio of ammonia to carbon dioxide is from about 1:2to about 3:1, or from about 1.5:1 to about 1:1.5, or from about 1.25:1to about 1:1.25, or even about 1:1. These molar ratio conditions can beextremely suitable for producing urea and its derivatives in furtherprocessing steps. Moreover, as shown by the molar ratios above a largeamount of captured carbon dioxide can be put to use to make a usefulproduct as opposed to disposal in some manner.

In another embodiment the decomposing of the second solution ischaracterized by decomposing in the absence of high temperature, theabsence of high pressure, or the absence of both. Specific temperaturesand pressures will vary depending upon the composition and the equipmentas well as, the desired further products, if any. The decomposing of thesecond solution in this embodiment can generally be accomplished at apressure of from about 0.75 atmospheres to about 1.25 atmospheres, oreven at about 1 atmosphere in many circumstances. Similarly, atemperature of less than about 80° C., or less than about 70° C., orless than about 60° C., or less than about 55° C., or less than about50° C., or less than about 45° C., or even as low as about 40° C. may beemployed depending upon the pressure. In this manner low grade heatgenerated in this process or from another process may be employed.Suitable sources for such low grade heat include, for example, flue gasheat, power plant heated run-off water, Kalina cycles, organic rankinecycles, geothermal gradients, ocean depths, diurnal temperaturevariations, solar power, various other waste heat sources, etc. In thismanner, heat that would otherwise go unused in many cases along withcaptured carbon dioxide that may otherwise be disposed may be employedin the process or other processes to generate electricity and usefulcompounds.

In another embodiment the decomposing of the second solution ischaracterized by decomposing in the presence of a semipermeable membranesuch as gas separation membrane to form substantially separated ammoniaand carbon dioxide. In this embodiment a semipermeable membrane isemployed wherein one or the other, but not both, ammonia or carbondioxide may migrate through the semipermeable membrane such thatsubstantially separated ammonia and carbon dioxide is formed. Suchsemipermeable membranes are known in the art and include, for example,those described in, for example, Toy et al. “CO₂ Capture MembraneProcess for Power Plant Flue Gas” Final Technical Report for Period ofPerformance: Oct. 1, 2008 to Sep. 30, 2011, published pursuant to DOECooperative Agreement No. DE-NT0005313 which paper is incorporatedherein by reference.

In some instances, it may be useful to, for example, heat the secondsolution to its decomposition temperature, e.g., at least about 41° C.at standard pressure, in a sealed container separated by a semipermeablemembrane from an aqueous third solution. The third solution may have alower osmotic pressure than the second solution, e.g., water or watercomprising salts such as NaCl. In this manner even though the secondsolution is heated above the decomposition temperature there is littleto no decomposition gases formed because of the sealed container with alack of headspace for formation. If, for example, carbon dioxide is thencontacted with said third aqueous solution at a lower temperature than41° C., then aqueous ammonia will, under suitable conditions, oftenmigrate across said semipermeable membrane from said second solution tosaid third aqueous solution across the membrane. Current membranessometimes have difficulty rejecting non-ionic ammonia species (e.g.,NH_(3(aq))) allowing them to migrate or diffuse in a similar manner towater. Said contacting with carbon dioxide may involve bubbling capturedcarbon dioxide or otherwise exposing carbon dioxide to the third aqueoussolution. Advantageously, this may convert at least a portion of thethird solution to one comprising ammonium carbonate, ammoniumbicarbonate or mixture thereof. This solution or a portion of it may inturn be recycled for use as the draw solution for the osmotic engine.The second solution then comprises carbonic acid and when depressurizedyields carbon dioxide gas suitable for any purpose and a solution whichis suitable for use as a feed solution in the same or another osmoticengine.

Alternatively, instead of contacting carbon dioxide with third aqueoussolution at a lower temperature than 41° C., the third solution may beheated or kept at substantially the same temperature as the secondsolution which is heated to at least about 41° C. In this manner,aqueous ammonia may be separated from the third solution via anyconvenient method such as membrane distillation.

In yet another embodiment, the decomposing of the second solution ischaracterized by decomposing in the presence of condensing, e.g.,cooling. The conditions may be such that a substantial portion of theammonia is condensed while a majority of the carbon dioxide is notcondensed. In this manner, substantially separated ammonia and carbondioxide are formed. Said condensing may be accomplished in anyconvenient manner. Suitable condensing includes, for example, cryogeniccooling, compression, etc.

In some instances it may be advantageous to decompose the secondsolution in the presence of a water-soluble, preferably non-azeotropic,solvent. Use of a non-azeotropic, solvent may facilitate the separationof solvents at a later time. Suitable solvents include those having aboiling point below that of water, e.g., acetone, methyl formate,ethanol, isopropyl alcohol, etc. In this manner under suitableconditions the solvent facilitates the release of carbon dioxide gasfrom the second solution and substantially separated ammonia and carbondioxide may be formed. This is typically employed when the secondsolution has a less than or equal to 1M concentration of ammoniumbicarbonate.

If desired, the decomposing of the second solution may be accomplishedunder conditions to form a precipitate which is then readily separablefrom the solution. Such precipitates include a salt of carbonate,carbamate, bicarbonate, or a mixture thereof. The specific manner ofprecipitate formation is not particularly important. In one embodiment asolvent is added to the second solution. This is typically employed whenthe second solution has a greater than or equal to 1M concentration ofammonium bicarbonate. In another embodiment a semipermeable membrane maybe employed between the second solution and an aqueous third solutionhaving a higher osmotic pressure, e.g., highly concentrated salt orother aqueous solution. In this manner, suitable precipitates, e.g.,ammonium bicarbonate precipitate, are formed which may be removed in anyconvenient way such as by decanting, filtering, screening, orcentrifuging. This is particularly effective when the second solutionhas a greater than or equal to 1M concentration of ammonium bicarbonate.The precipitate may then be employed in any useful manner such as makinga further draw solution for the osmotic engine.

Use of Decomposed Second Solution

Generally, once separated the carbon dioxide and ammonia can be reusedin the instant process or used elsewhere. For example, the ammonia maybe employed to capture further carbon dioxide. The separated carbondioxide gas may be used in, for example, enhanced oil recovery, disposedinto saline aquifers, utilized in the accelerated weather of limestoneprocess or used in other commercial or non-commercial application,including, but not limited to dry ice production. If desired, theammonia and carbon dioxide may be employed to make a useful or salableproduct, e.g., ammonium carbamate which is useful to make urea which maybe used to make cyanuric acid. Such procedures are described in, forexample, Barzagli et al., Green Chem., 2011, 13, 1267-1274 which isincorporated herein by reference.

Use of Redox Battery

If desired a redox battery may be implemented into the process at asuitable place to generate electricity. Typically, the place where it isemployed depends upon the specific system. Generally, if a redox batteryis employed then it may be located across a heat exchanger. If apressure retarded osmosis membrane is employed then a redox battery maybe employed prior to or alternatively after such a membrane.

If employed, then the battery is typically selected from an ammonia,ammonium carbonate or ammonium bicarbonate redox battery. Such batterieswill typically employ a suitable metal as the anode and the cathode.Such metals include, for example, copper, zinc, nickel, silver, lead,cobalt, and mixtures thereof. Copper may be particularly preferable forsome applications. In this manner ammonia or ammonium may react with themetal at the anode to produce a water soluble complex cation. At thecathode the solution may be decomposed using, for example, low gradeheat which causes a solid metal to deposit. DC electricity is generatedby completing the circuit via connecting the electrodes with, forexample, a wire. The electrodes may be periodically swapped to ensurethe electrode in the oxidation solution does not become too depleted.Suitable batteries are described in, for example, Energy Environ. Sci.,2015, 8, 343 Zhang et al., “A thermally regenerative ammonia-basedbattery for efficient harvesting of low-grade thermal energy aselectrical power.”

EXAMPLES OF SPECIFIC EMBODIMENTS Example 1 Pressure Retarded OsmosisWaste Heat Recovery System with Carbon Capture Using Pressurization andDepressurization

A specific embodiment of the instant invention is shown in FIG. 1. Inthis embodiment low grade heat is used to simultaneously capture carbondioxide and generate electricity using osmotic gradients engineeredusing a heat exchange process. As shown, flue gas comprising carbondioxide is contacted with ammonia to form the High ConcentrationSolution. The High Concentration Solution is used as a draw solution andcomprises ammonium carbonate, ammonium bicarbonate or mixture thereofformed from at least a portion of captured carbon dioxide. The heatexchange process uses a pressurization and depressurization system,which pressurizes the system to release CO_(2(g)) during carbon captureand depressurizes the system to release NH_(3(g)) to recreate the highconcentration draw solution.

Specifically, pressure retarded osmosis (PRO) and a thermolytic salt(e.g. ammonium bicarbonate or trimethylamine-carbon dioxide) areemployed. The system can run the electricity generation, carbon captureand other related processes simultaneously, although different aspectsof the system may be conducted at different time or rates. The systemmay also utilize reverse electrodialysis, nano battery electrodes, orultra capacitors (CAPMIX) to generate electricity from concentrationgradients in the electricity generation process.

The carbon capture process involves allowing the heat exchange region topressurize during the heat exchange process. At a higher pressure,NH_(3(g)) stays in solution, while the headspace contains mostlyCO_(2(g)). A valve or other gas release mechanism is opened from thecontainer that allows headspace gas (mostly composed of CO_(2(g))) to bereleased, while keeping the container pressurized. A gas turbine may beused to keep the system pressurized and generate electricity from theCO_(2(g)) expansion. The system can be pressurized through thecontainment of the decomposition gases and/or through the use of a pumpor other device to pressurize the system. The gas (mostly composed ofCO_(2(g))) is bubbled through water to remove traces of NH_(3(g)) gasand is in a pure form. The CO_(2(g)) is now ready for sale, storage,industrial chemical synthesis and/or other purposes.

After a significant amount of CO_(2(g)) is released, the system isdepressurized. The system can be depressurized through the release ofdecomposition/headspace gases and/or through the use of a pump, vacuumpump or other device to depressurize the system. The depressurization ofthe system allows for the release of NH_(3(g)) from the solution, and alower concentration of CO_(2(g)). A gas stream mixture of a highconcentration of NH_(3(g)) and low concentration of CO_(2(g)) is thenrecycled to recreate the HC solution through reaction with CO_(2(g)) ina gas stream, including, although not limited to, flue gas, anaerobicdigester gas, waste facility gas, ambient air or other treated oruntreated CO_(2(g)) containing gases.

Example 2 Forward Osmosis Waste Heat Recovery System with Carbon CaptureUsing Pressurization and Depressurization

Another specific embodiment of the instant invention is shown in FIG. 2.The system previously described above in Example 1 can be used as aforward osmosis water purification/desalination process that recoversheat in the system through electricity production, water desalination,and carbon capture. The system in Example 1 can be converted to aforward osmosis process by utilizing saline water (e.g. sea water orwaste water) as the LC feed solution and sending desalinated water outof the system for sale or other purpose following the heat exchangeprocess, rather than recycling the water to replenish the feed/LCsolution. The system has all of the functionalities of the system inexample 1 and desalinates water through forward osmosis.

Example 3 Pressure Retarded Osmosis Waste Heat Recovery System withCarbon Sequestration Through the Production of Urea

Another specific embodiment of the instant invention is shown in FIG. 3.The system uses low grade heat to simultaneously generate electricity,and capture and sequester CO₂ in the form of ammonium carbamate, whichis subsequently converted to urea. The pressurization anddepressurization heat exchange process is employed to concentrate NH₃and capture excess CO₂. The concentrated NH₃ and low concentration CO₂gas stream created in the heat exchange process is contacted with anorganic solvent to react and form ammonium carbamate.

The system continuously feeds NH_(3(g)) and CO_(2(g)) to recreate the HCdraw solution in the electricity generation process. Therefore, in aversion of the ammonium carbamate/urea production system, NH₃ is notrecycled, although NH₃ may be recycled or recovered if desired. Theconcentrated NH₃ and lower concentration CO₂ (Note: the concentration ofCO₂ could be equal to or greater in concentration than the NH₃, althougha higher concentration of NH_(3(g)) is preferred) gas stream iscontacted with an organic solvent, which dissolves both NH₃ and CO₂,resulting in the gases reacting to form ammonium carbamate and/or amixture comprising ammonium carbamate, ammonium carbonate and/orammonium bicarbonate. The ammonium carbamate can be separated throughprecipitate removal methods, including, although not limited to, filter,screen, centrifuge, etc., and/or can be removed from solution throughdistillation of the solvent to remove dissolved ammonium carbamate.

If desired, the ammonium carbamate byproduct can be converted to ureavia various processes, sold on its own, and/or converted into othercompounds. The urea can also be converted into compounds that releaseNH₃ during synthesis, such as cyanuric acid, and/or compounds thatabsorb additional CO₂ during their synthesis. This could allow foradditional NH₃ recovery/recycling and/or CO₂ sequestration.

Example 4 Forward Osmosis Waste Heat Recovery System with CarbonSequestration Through the Production of Urea

Another specific embodiment of the instant invention is shown in FIG. 4.This example is similar to Example 3 except that saline water is used asthe feed solution. Example 4 employs a similar heat recovery system thatgenerates electricity and captures and sequesters CO₂ in the processdescribed in Example 3, except desalinates water through forwardosmosis. In this system, saline water and/or waste water is used as thefeed solution and desalinated, purified water is produced as theremaining substance following the decomposition of aqueous ammoniumcarbonate, ammonium bicarbonate, ammonium carbamate or mixture thereofin the heat exchange process. This system allows for heat recoverythrough simultaneous and integrated/interconnected electricitygeneration, water desalination, carbon capture and sequestration andammonium carbamate and other chemical synthesis.

Example 5 Higher Efficiency Pressure Retarded Osmosis Waste HeatRecovery System Through Addition of Water Soluble Organic Solvent toPrecipitate Ammonium Bicarbonate Solid from Aqueous Solution

Another specific embodiment of the instant invention is shown in FIG. 5.A heat recovery process that generates electricity from an engineeredconcentration gradient using the processes generally described inExample 1, except uses a novel method to reform the concentrationgradient. The system engineers the concentration gradient through theaddition of a water soluble solvent to the ammonium bicarbonate solution(generally >=1M aqueous ammonium bicarbonate concentration) toprecipitate the ammonium bicarbonate as a solid. It is usually desirablethat the solvent added is a non-azeotropic, water soluble, low boilingpoint substance, such as acetone or methyl formate. Other solvents maybe effective that do not have some or all of the previously describedproperties, including, although not limited to isopropyl alcohol andethanol, although may be less favorable depending upon the systemspecifics.

The ammonium bicarbonate precipitate is removed through a liquid-solidseparation method, including, although not limited to filtration, theuse of a centrifuge and other processes. The separated solid ammoniumbicarbonate is transferred/recycled to concentrate the HC solutionthrough dissolution. The organic solvent is removed from thewater-solvent mixture remaining following precipitate separation processthrough fractional distillation or other method, removing the addedsolvent from the water. The water is used to replenish the lowconcentration feed solution, while the organic solvent vapor iscondensed for reuse.

A gas turbine may be used to generate electricity from the gas expansionduring the distillation process. The entire system allows forelectricity production from waste heat through an Osmotic Heat Enginewith a unique organic solvent ammonium bicarbonate precipitation systemof engineering the concentration gradient that reduces energyconsumption and improves energy efficiency. The system is generally mosteffective when the concentration of the diluted HC draw solution is >1M.

Example 6 Higher Efficiency Forward Osmosis High Concentration WaterDesalination and Waste Heat Recovery System Through Addition of OrganicSolvent to Precipitate Ammonium Bicarbonate Solid from Aqueous Solution

Another specific embodiment of the instant invention is shown in FIG. 6.Example 6 is similar to Example 5 except uses saline water as the feedsolution, converting the process into a forward osmosis waterdesalination system. The water soluble organic solvent addition systemcould significantly reduce the energy consumption and increase theefficiency of the desalination of very concentrated water.

A heat recovery system that utilizes the processes described in Example5 for electricity generation, except uses saline water, including,although not limited to sea water, waste water or frac water, as thefeed solution in a forward osmosis water desalination process. Freshwater is removed from the saline water feed solution via engineeredosmosis through the creation of a concentration gradient in the presenceof a semipermeable membrane. Purified, desalinated water is produced asa byproduct following the fractional distillation step, which removesthe organic solvent from water using heat. The system is especiallyuseful in desalinating very saline solutions because of its ability toconvert the high concentration draw solution into pure water and solidammonium bicarbonate with very little energy consumption.

Unlike current forward osmosis processes, which usually requiredecomposing all of the aqueous ammonium bicarbonate into itsdecomposition gases using low grade heat, this system's only energyconsuming step involves boiling the proportionally minuscule amount oflow boiling point organic solvent out of an aqueous solution during thedistillation step, which requires significantly less energy. This systemuses low grade heat to simultaneously generate electricity, whiledesalinating concentrated water at a greater efficiency than currentforward osmosis processes.

Example 7 Pressure Retarded Osmosis Waste Heat Recovery and CarbonCapture System Through Addition of Water Soluble Organic Solvent toDecompose Ammonium Bicarbonate

Another specific embodiment of the instant invention is shown in FIG. 7.Example 7 is a low grade heat recovery system that generates electricityand captures carbon dioxide. The system utilizes the addition of a lowboiling point organic solvent to a low concentration ammoniumbicarbonate solution (<1M) to decompose the salt into CO_(2(g)) andNH_(3(aq)).

A heat recovery process that generates electricity from an engineeredconcentration gradient using the processes described in Example 1,except uses a novel method to reform the concentration gradient andcapture carbon dioxide. When a highly water soluble organic solvent isadded to a low concentration aqueous ammonium bicarbonate solution, theammonium bicarbonate decomposes, releasing CO_(2(g)), while NH_(3(aq))remains in the solution. This is different from the process described inExample 5 and 6, which involve the addition of an organic solvent to ahigher concentration ammonium bicarbonate solution (>1M typically),which results in solid ammonium bicarbonate precipitating and notdecomposing. When a water soluble organic solvent is added to a lowconcentration ammonium bicarbonate_((aq)) solution, the ammoniumbicarbonate decomposes, while in a high concentration solution, theammonium bicarbonate precipitates out as a solid. Example 7 uses thedecomposition of a low concentration ammonium bicarbonate solution toreform the concentration gradient and capture carbon dioxide.

Following the Osmotic Heat Engine electricity generation process, adilute ammonium bicarbonate solution is transferred to the water solubleorganic solvent addition process. In this process, a water solubleorganic solvent is added to the solution, resulting in the release ofCO_(2(g)) from the decomposition of ammonium bicarbonate. This CO_(2(g))can be bubbled through water to remove the organic solvent vapors due tovapor pressure and is then purified and captured. The CO_(2(g)) can thensold, stored, used in enhanced oil recovery, or for any other use. Oncethe CO_(2(g)) has left the original solution, the remaining solution,which is likely made up of water, the added organic solvent, a highconcentration of NH₃, and a low concentration of CO_(2(g)), isfractionally distilled to separate the organic solvent and NH₃ from thewater. The water is used to replenish the LC feed solution, while theNH_(3(g)) and the organic solvent vapors are separated by condensing theorganic solvent, while the NH_(3(g)) passes through. The NH_(3(g)) isused to recreate the HC solution through reaction with CO_(2(g)) fromsources, including, although not limited to flue gas, and the organicsolvent is recycled. To prevent the organic solvent vapor (resultingfrom vapor pressure) from contaminating the HC solution, the organicsolvent+NH_(3(g)) mixture can be bubbled through a low vapor pressure,nonpolar liquid which is less dense than the organic solvent at a liquidstate. This nonpolar liquid will condense the organic solvent, allowingit to settle below the nonpolar liquid, while the NH_(3(g)) bubblesthrough containing no organic solvent vapor.

Example 8 Integrated Process

This example is similar to Example 7 as it relates to an ammoniumcarbamate process. However, in Example 8 the process is integrated witha forward osmosis process, urea production, and/or a combination thereofin a similar fashion to the methods described in Example 1-4.

Example 9 Membrane Carbon Capture

Another specific embodiment of the instant invention is shown in FIG. 8.In this continuous process example flue gas with from approximatelyabout 10 to about 20 percent of carbon dioxide is captured with aqueousammonia that is diffusing through a pressure retarded osmosis membraneand forms an aqueous solution of ammonium carbonate, ammoniumbicarbonate, ammonium carbamate, or mixture thereof. The aqueous ammoniaused is generated by heating the aqueous ammonium solution to itsdecomposition temperature. The remaining flue gas may then be routed toa carbon dioxide absorption column where additional carbon dioxide maybe captured via contact with a middle concentrated solution and theresulting ammonium solution used as draw solution with a pressureretarded osmosis membrane to generate electricity and a dilute solution.The electricity generated may be sold or for other uses while thediluted solution may be recycled. Separated carbon dioxide gas generatedmay be employed in any useful process.

Example 10 Urea Production

Another specific embodiment of the instant invention is shown in FIG. 9.This example is similar to that described above in Example 3 except thatfrom the heat exchanger a portion of the carbon dioxide gas may beoptionally recycled to the high concentration draw solution and the lowconcentration solution may be recycled to capture carbon dioxide fromflue gas. Advantageously, in this example ammonia gas and carbon dioxidegas are generated at the heat exchanger in a suitable molar ratio forammonium carbamate synthesis and conversion to urea.

Example 11 Urea Production Using Common Ion Precipitation

Another specific embodiment of the instant invention is shown in FIG.10. This example is similar to that described above in Example 10 exceptthat the high concentration draw solution is formed via a common ionprecipitation method. In such a method ammonia gas, carbon dioxide gasand water react to form an ammonium bicarbonate precipitate.Specifically, flue gas and ammonia may react to form a highconcentration common-ion draw solution that can be used as part of acontinuous forward osmosis process as shown in the figure. Anyprecipitates formed can be mixed with a low concentrated solution toform the high concentration draw solution for the pressure retardedosmosis osmotic engine.

Example 12 Integrated Process and System for Simultaneous Heat Recovery,Carbon Capture/Sequestration, and Urea Production

This example is an integrated process/system for simultaneous heatrecovery, carbon capture/sequestration and urea production. The systemcomprises five components: 1) absorption of carbon dioxide; 2)electricity generation from concentration gradients; 3) solutiondecomposition; 4) ammonium carbamate production; and 5) urea production.

Component 1:

In the first component, there are two routes for absorbing carbondioxide gas: 1) direct carbon dioxide gas absorption; 2) gas absorptionby common-ion ammonium bicarbonate, carbonate salt precipitation. Eitherof these routes or even a combination can be employed.

1. Direct Carbon Dioxide Gas Absorption:

In the integrated process, regenerated low concentration (LC) or middleconcentration (MC) solution is transferred into an absorption column.The solution will usually be either LC or de-ionized water when thedecomposition step in the integrated process (Component 3) uses thermaldecomposition with low grade heat under atmospheric pressure or ambientsystem pressure. When Component 3 is a semi-permeable membrane basedcarbon capture process, then the solution will usually be a middleconcentration (e.g. from about 0.05 to about 1M ammonium bicarbonatesolution).

Ammonia gas is released into the absorption column where it is absorbedby the LC or MC solution to form an aqueous ammonia solution. Whenammonia is absorbed by LC solution, the solution will typically beaqueous ammonia. When ammonia is absorbed by MC solution, the solutionwill typically be aqueous ammonia:carbon dioxide species at an NH₃:CO₂molar ratio of from about 1:1 to about 10:1.

A gas stream containing carbon dioxide (e.g. flue gas, methane reforminggas) is released into the absorption column, where it reacts with theaqueous ammonia to form an aqueous ammonium-carbonate, bicarbonate,carbamate solution. The remaining inert gases (N_(2(g)), O_(2(g))) maybe released back into the atmosphere. In room temperature pressure (RTP)conditions, flue gas CO₂ absorption will form a solution at an NH₃:CO₂molar ratio of ˜3:1. This is described in, for example, Bai et al., Ind.Eng. Chem. Res., 1997, 36 (6), pp 2490-2493 incorporated herein byreference.

The <1.5:1 NH₃:CO₂ molar ratio used for Pressure Retarded Osmosis (PRO)membranes (Component 2) can be achieved by reducing the temperatures inthe absorption column (cooling via heat sink, such as ocean, lake orriver water) and/or recycling a portion of the carbon dioxide gasreleased in the solution decomposition (Component 3) to form a higherpartial pressure of carbon dioxide gas after the flue gas carbon dioxideabsorption, increasing the proportional amount of CO₂ in solution.Carbon dioxide in methane reforming gases following the low temperaturegas-shift is at a significantly higher partial pressure (˜2.98 bar, 16bar total pressure as described by Molberg et al. “Hydrogen fromSteam-Methane Reforming with CO₂ Capture” 20th Annual InternationalPittsburgh Coal Conference Sep. 15-19, 2003 Pittsburgh, Pa. incorporatedherein by reference) and, due to this higher solubility of carbondioxide, will not require CO₂ recycling.

2. Common-Ion Ammonium Bicarbonate, Carbonate Salt Precipitation:

In a separate osmotic heat engine or forward osmosis (FO) component, asalt solution containing a common ion, such as ammonium, carbonate,bicarbonate, carbamate, is employed as a draw solution. Such solutionsinclude, for example, ammonium sulfate, ammonium nitrate, potassiumcarbonate, or potassium bicarbonate. In this manner the presence of thecommon ion salt with a more soluble common ion will cause the lowersolubility ammonium bicarbonate to precipitate.

Once the draw solution becomes diluted during the PRO or FO, thesolution is sent into the absorption column. Ammonia and carbon dioxideare bubbled, sparged, or otherwise transferred through this aqueoussolution so as to react and form ammonium bicarbonate, ammoniumcarbonate, or a mixture thereof. Due to the common-ion effect from thepresence of the ammonium sulfate, ammonium nitrate, potassiumbicarbonate or potassium carbonate, the solubility of the solution ofammonium bicarbonate, ammonium carbonate or mixture is significantlyless than in a pure aqueous solution. This causes the salt comprisingammonium bicarbonate, ammonium carbonate or mixture to more readilyprecipitate out of solution.

The salt of ammonium bicarbonate, ammonium carbonate or mixtureprecipitates with the removal of a water via the following reactions:NH_(3(aq))+CO_(2(aq))+H₂O_((l))→VH₄HCO_(3(s));  1)2NH_(3(aq))+CO_(2(aq))+H₂O_((l))→(NH₄)₂CO_(3(s)).  2)The precipitate may be filtered continuously from the common-ion saltsolution and transferred to an ammonium carbonate, ammonium bicarbonateosmotic engine, where it can be dissolved in regenerated LC or MCsolutions to form the draw solution for the process. Additionally oralternatively, the precipitate can also be sent directly to Component 3,where it may be decomposed with low grade heat into NH_(3(g)) andCO_(2(g)) (which are reacted to form ammonium carbamate) and pureH₂O_((l)). Over time enough water may be removed by the saltprecipitation of ammonium carbonate, ammonium bicarbonate or mixturethat the common-ion salt solution becomes sufficiently concentrated tobe recycled as a draw solution.

Component 2:

The electricity generation component (Component 2), if included, can beconducted via three main methods or it can be absent from the process.In the instance where it is absent from the process, the solution formedin Component 1 is typically transferred directly to Component 3, wherethe solution is decomposed.

1. Electricity Generation using Pressure Retarded Osmosis (PRO):

The <1.5:1 NH₃:CO₂ molar ratio solution created in Component 1 is usedas a draw solution. As shown in FIG. 12 at an NH₃:CO₂ molar ratio of1.5:1, the solution has a pH of ˜>8.5 at a temperature of 298K. PRO ismost effective when ionic NH4+ species are present. NH_(3(aq))(non-ionic species) acts in a similar manner to water with PROmembranes. The LC or de-ionized solution regenerated in the integratedprocess is used as a feed solution. Separating the draw and feedsolutions is a PRO membrane, a thin-film composite (TFC) membrane madeup of a selective polyamide and a polysulfone support layer. Suitablemembranes are described in, for example, Yip et al., Environ. Sci.Technol., 2011, 45 (10), pp 4360-4369 which is incorporated herein byreference.

Water moves from the LC feed solution to the draw solution due to thenatural force of osmosis generated from the difference in osmoticpressure between the two solutions. The flow of water across themembrane is fed into a hydroelectric turbine to generate electricity.The solution remaining after the hydroelectric turbine is a dilutedversion of the initial draw solution. This solution is transferred toComponent 3 to decompose the solute and regenerate the LC or MCsolutions.

2. Further Electricity Generation Through Employing a Copper-AmmoniumCarbonate, Bicarbonate Redox Battery Following PRO (FIG. 11):

The diluted ammonia-carbon dioxide draw solution produced after PRO istransferred into a solution in contact with a copper electrode (can alsobe, for example, Zinc, Nickel, Silver, Lead, Cobalt). The ammoniaspecies reacts (oxidation) with the copper electrode (anode) to form awater soluble complex cation. The solution is then transferred to theheat exchanger in Component 3 (either in a continuous or in a batchsystem), where another copper electrode (cathode) is present insolution. The solution is decomposed using low grade heat in the heatexchanger, causing solid copper (Cu_((s))) to be deposited on the copperelectrode/cathode (reduction). As the copper electrode in the complexion formation solution is oxidized and the copper electrode in the heatexchange is reduced, DC electricity is generated by connecting theelectrodes with, for example, wire, thereby forming a complete circuit.The electrodes may be periodically swapped between solutions to ensurethe copper electrode in the oxidation solution does not become toodepleted.

FIG. 11 depicts a diagram of the system wherein a novel regeneratedcopper-ammonium carbonate, bicarbonate battery is employed to generateadditional electricity in the process. Copper is oxidized in thecomplex-ion formation solution and is reduced in the thermaldecomposition solution (heat exchange), generating DC electricity.Copper solid is removed/depleted from the copper electrode in the CopperOxidation solution and deposited on the copper electrode in the CopperReduction solution. The electrodes may be switched between solutionsperiodically to ensure the copper electrode in the oxidation solutionnever becomes too depleted.

3. Electricity Generation from Employing a Copper-Ammonium Carbonate,Bicarbonate Redox Battery (Membrane-Free Process) (FIG. 12):

The ammonia-carbon dioxide solution produced in component 1 istransferred into a solution in contact with a copper electrode (can alsobe, for example, Zinc, Nickel, Silver, Lead, Cobalt). The ammoniaspecies reacts (oxidation) with the copper electrode (anode) to form awater soluble complex cation. The solution is transferred to the heatexchanger in Component 3 (either in a continuous or in a batch system),where another copper electrode (cathode) is present in solution. Thesolution is decomposed using low grade heat in the heat exchanger,causing solid copper (Cu_((s))) to be deposited on the copperelectrode/cathode (reduction). As the copper electrode in the complexion formation solution is oxidized and the copper electrode in the heatexchange is reduced, DC electricity is generated by connecting theelectrodes with wire, forming a complete circuit. The electrodes may beperiodically swapped between solutions to ensure the copper electrode inthe oxidation solution never becomes too depleted.

FIG. 12 depicts a diagram of the system wherein a membrane-lessvariation of the system in FIG. 11 generates electricity and valuablenitrogen compounds. This variation of the system generates electricitywith a regenerated copper-ammonium carbonate, bicarbonate battery, whileadvantageously continuing to produce an ammonia-carbon dioxide gasmixture at a suitable molar ratio for ammonium carbamate synthesis.

4. Further Electricity Generation Through Employing a Copper-AmmoniumCarbonate, Bicarbonate Redox Battery Prior to PRO (FIG. 13).

FIG. 13 depicts a variation of the above systems that generateselectricity and captures carbon dioxide. This variation of the systemgenerates electricity with a regenerated copper-ammonium carbonate,bicarbonate battery, while capturing carbon dioxide using an aqueoussemipermeable membrane.

PRO Effectiveness

As shown in FIG. 14, at an NH₃:CO₂ molar ratio of 1.5:1, the solutionhas a pH of about 9 at a temperature of 298K. Pressure retarded osmosisis generally effective when NH4+ species are present. NH_(3(aq))(non-ionic species) often acts in a similar manner to water with mostPRO membranes.

5. Electricity Generation Using Reverse Electro Dialysis (RED):

The ammonia-carbon dioxide species solution created in component 1 isused as a concentrated solution while the LC or de-ionized watersolution regenerated in the integrated process is used as the opposingsolution. The solutions are separated by stacked anion and cationexchange membranes (AEM and CEM). On the ends of the stack, there is ananode and a cathode. Electricity is generated when the net negativechange produced by the AEM and the net positive charge produced by theCEM is neutralized by the anode and cathode in a DC circuit. Suchmethods are described in, for example, Paripati et al., US 20140026567which is incorporated herein by reference.

6. Other Methods to Generate Electricity from Aqueous ConcentrationGradients (e.g. CAPMIX):

There are other methods for generating electricity from concentrationgradients, including capacitive mixing power production (CAPMIX). Thesemethods include the use of Nano-Battery Electrodes (NBE), CapacitiveDouble Layer Expansion (CDLE), and/or Capacitors Charged by the DonnanPotentials (CDP). These methods are described in, for example, EnergyProcedia, Volume 20, 2012, Pages 108-115 Technoport 2012—SharingPossibilities and 2nd Renewable Energy Research Conference (RERC2012)CAPMIX—Deploying Capacitors for Salt Gradient Power Extraction; M. F. M.Bijmans, et al. which is incorporated herein by reference.

Component 3:

Involves the decomposition of the solution created in Component 2 or theprecipitate formed in Component 1 in any convenient manner such as oneof the four described below or a combination thereof.

1. Low Grade Temperature Thermal Decomposition under System PressureConditions:

The diluted solution created in Component 2 or the precipitate createdin Component 1 may be decomposed into ammonia and carbon dioxide gasesat the decomposition temperature of the ammonium carbonate, ammoniumbicarbonate or mixture at a system pressure of from about 0.75 to 1.25atm. The decomposition of the ammonium carbonate, ammonium bicarbonateor mixture solution involves the initial release of carbon dioxide gas,with substantially less ammonia gas being released. A portion of thishigher partial pressure carbon dioxide gas stream can be recycled backto Component 1 and/or Component 2 to generate a solution with an NH₃:CO₂molar ratio <1.5:1 for PRO energy generation. This gas stream can alsobe condensed via compression and/or cryogenic cooling to producesubstantially separated liquid ammonia and carbon dioxide gas with insome cases a small quantity of ammonium carbamate precipitate. Overtime, a higher partial pressure of ammonia gas begins to release fromsolution, at which point the gas mixture created can be transferred toComponent 4 for ammonium carbamate production. Advantageously, thisprocess requires less work energy than current carbon capture processes,including the chilled ammonia process, due to the lack of a higherpressure and temperature (80-110 C) equilibrium, which is required inthese carbon capture processes as described by Yeh, J., & Pennline, H.(2004), Absorption and regeneration studies for CO₂ capture by aqueousammonia, Third Annual Conference on Carbon Capture & Sequestration. Thisequilibrium is not required in this route because the gas streamproduced is an ammonia and carbon dioxide gas mixture at a suitablemolar ratio for ammonium carbamate/urea production, not pure carbondioxide gas.

2. Using Aqueous Semi-Permeable (e.g. PRO) Membrane Under Low GradeTemperatures to Separate Ammonia and Carbon Dioxide:

This route significantly reduces the energy consumption involved withcarbon capture by reducing the need to thermally convert ammonia fromits aqueous species to a gaseous species (very energy intensiveprocess). Additionally, it leaves aqueous carbon dioxide in solutionwithout an accompanying Ammonia species (i.e. NH₃:CO₂ molar ratio <1:1),causing pure Carbon Dioxide to come out of the solution readily underRTP conditions.

The solution created in Component 2 is transferred into a closed chamberwhere it is in contact with a semi-permeable membrane, such as the PROmembrane described in Component 2. This solution is heated to thedecomposition temperature of the solute of ammonium carbonate, ammoniumbicarbonate or mixture, although the constituents of the solute do notcome out of the solution as gases because of the closed chamber.Instead, the ammonia and carbon dioxide stay in solution as NH_(3(aq))and CO_(2(aq)) species (non-ionic forms). On the other side of thesemi-permeable membrane is cooled dilute carbonic acid solution (e.g.10° C.) sparged with flue gas containing carbon dioxide (of which asmall portion dissolves, forming the dilute carbonic acid, or CO_(2(aq))solution). The semipermeable membrane rejects the CO_(2(aq)) speciesfrom diffusing because of its larger molecule size and dissimilarproperties to that of water, while the NH_(3(aq)) species (havingsimilar molar mass and properties to that of water) is not rejected bythe membrane (attribute of PRO membranes). The NH_(3(aq)) diffusesacross the membrane into the dilute carbonic acid solution, where itreacts to form aqueous ammonium carbonate or ammonium bicarbonate.Eventually, the solution that forms in this reaction is transferred toComponent 1 as a middle concentration (MC) solution. A valve is openedabove the solution on the opposing side of the semi-permeable membrane(now containing more CO_(2(aq)) than NH_(3(aq)) species due to thediffusion of NH_(3(aq)) species across the semipermeable membrane),causing the solution to depressurize. Carbon dioxide gas comes out ofsolution under RTP/ambient conditions and is pure for use. Thisdepressurization will likely cause a rapid drop in temperature of thesolution, which has application in cooling, including cooling Component1 to increase the rate of absorption. The remaining solution after theCO_(2(g)) has been released is heated using low grade heat to remove andrecycle any remaining NH_(3(aq)) species and is transferred to Component2 as an LC solution.

3. Water Soluble Solvent Carbon Dioxide and Ammonia Separation:

Following Component 2, a dilute ammonium bicarbonate solution istransferred to the water soluble organic solvent addition process. Inthis process, a water soluble organic solvent is added to the solution,resulting in the release of CO_(2(g)) from the decomposition of ammoniumbicarbonate. This CO_(2(g)) can be bubbled through water to remove theorganic solvent vapors due to vapor pressure and is then purified andcaptured. The CO_(2(g)) can then sold, stored, used in enhanced oilrecovery, or for any other use. Once the CO_(2(g)) has left the originalsolution, the remaining solution, which is likely made up of water, theadded organic solvent, a high concentration of NH₃, and a lowconcentration of CO_(2(g)), is fractionally distilled or uses membranedistillation (MD) to separate the organic solvent and NH₃ from thewater. The water is used to replenish the LC feed solution, while theNH_(3(g)) and the organic solvent vapors are separated by condensing theorganic solvent, while the NH_(3(g)) passes through. The NH_(3(g)) isused to recreate the HC solution through reaction with CO_(2(g)) fromsources, including, although not limited to flue gas, and the organicsolvent is recycled. To prevent the organic solvent vapor (resultingfrom vapor pressure) from contaminating the HC solution, the organicsolvent+NH_(3(g)) mixture can be bubbled through a low vapor pressure,nonpolar liquid which is less dense than the organic solvent at a liquidstate. This nonpolar liquid will condense the organic solvent, allowingit to settle below the nonpolar liquid, while the NH_(3(g)) bubblesthrough containing no organic solvent vapor.

4. Water-Soluble Organic Solvent Ammonium Bicarbonate, Carbonate,Mixture Thereof Precipitation:

The system engineers the concentration gradient through the addition ofa water soluble solvent to the ammonium carbonate, bicarbonate mixturesolution (generally >=1M aqueous ammonium bicarbonate concentration) toprecipitate the ammonium bicarbonate as a solid. It is usually desirablethat the solvent added is a non-azeotropic, water soluble, low boilingpoint substance, such as acetone or methyl formate. Other solvents maybe effective that do not have some or all of the previously describedproperties, including, although not limited to isopropyl alcohol andethanol, although may be less favorable depending upon the systemspecifics.

The ammonium bicarbonate precipitate is removed through a liquid-solidseparation method, including, although not limited to filtration, theuse of a centrifuge and other processes. The separated solid ammoniumbicarbonate is transferred/recycled to concentrate the HC solutionthrough dissolution. The organic solvent is removed from thewater-solvent mixture remaining following precipitate separation processthrough fractional distillation or other method, removing the addedsolvent from the water. The water is used to replenish the lowconcentration feed solution, while the organic solvent vapor iscondensed for reuse.

A gas turbine may be used to generate electricity from the gas expansionduring the distillation process. The entire system allows forelectricity production from waste heat through an osmotic heat enginewith a unique organic solvent ammonium bicarbonate precipitation systemof engineering the concentration gradient that reduces energyconsumption and improves energy efficiency. The system is generally mosteffective when the concentration of the diluted HC draw solution is >1M.The system can also be used for lower work energy consumptiondesalination by using saline water as a feed solution and forwardosmosis semipermeable membrane instead of a PRO membrane.

Component 4:

This component generally involves reacting the ammonia and carbondioxide gases generated in Component 3 to produce ammonium carbamate, anessential precursor/intermediate in urea production. Ammonium carbamateproduction processes currently used in urea production plants areemployed in this component. Advantageously, Component 3 may produce theNH_(3(g)) and CO_(2(g)) at the appropriate molar ratio for the specificammonium carbamate synthesis process being employed. Current methodsinclude contacting the gases directly in a gas compression system.Processes for producing ammonium carbamate include sparging theNH_(3(g)) and CO_(2(g)) into an organic solvent at a 1-2:1 NH₃:CO₂ molarratio in a continuous flow reactor as described in, for example,Barzakli et al., Green Chem., 2011, 13, 1267-1274 which is incorporatedherein by reference. Other compounds may be added to the gas stream orsolutions. For example, methanol, may be added as it can be reacted withammonia to form methylamine, dimethylamine and trimethylamine, withpotential application in pesticides and pharmaceuticals. Suchtrimethylamine also may potentially be used as draw solutions asdescribed in, for example, Boo et al., Journal of Membrane Science,Volume 473, 1 Jan. 2015, Pages 302-309 which is incorporated byreference herein.

Component 5:

Component 5 produces urea from ammonium carbamate (produced in Component4) or from ammonia and carbon dioxide gas mixtures. Such processes maybe conducted in any useful manner but advantageously the molar ratios ofthe substances produced in the present invention are particularly usefulfor Component 5.

The claimed subject matter is not to be limited in scope by the specificembodiments described herein. Indeed, various modifications of theinvention in addition to those described herein will become apparent tothose skilled in the art from the foregoing description. Suchmodifications are intended to fall within the scope of the appendedclaims.

What is claimed is:
 1. An integrated process for generating energy anduseful nitrogen compounds from captured carbon dioxide comprising:forming a solution of ammonium carbonate, ammonium bicarbonate, ammoniumcarbamate or mixture thereof wherein said solution is formed from atleast a portion of captured carbon dioxide; and decomposing the solutionof ammonium carbonate, ammonium bicarbonate, ammonium carbamate ormixture thereof to form a second aqueous solution comprising ammonia,carbon dioxide, or a mixture thereof; wherein the decomposing of thesolution to form said second aqueous solution is conducted in thepresence of a water soluble organic solvent to form a gaseous carbondioxide and aqueous ammonia in the absence of a precipitate.
 2. Theintegrated process of claim 1 wherein the captured carbon dioxide usedto form the solution comprises carbon dioxide captured from combustionor oxidation of one or more hydrocarbons, from steam reforming, from gasshift reaction, from catalytic reforming, from natural gas purification,from land fill gas, from biogas, from waste water treatment,fermentation, respiration, from air, or from mixtures thereof.
 3. Theintegrated process of claim 1 wherein the formation of the solution ischaracterized by the purification of gas streams containing hydrogen,methane, or other desired gas by capturing carbon dioxide in these gasstreams.
 4. The integrated process of claim 1 further comprisingproducing ammonium carbamate, urea, or a derivative thereof.
 5. Theintegrated process of claim 1 wherein the decomposing of the solution ischaracterized by decomposing at a pressure of from about 0.75atmospheres to about 1.25 atmospheres and a temperature of less thanabout 70° C.
 6. The integrated process of claim 1 wherein thedecomposing of the solution is characterized by decomposing at atemperature of from about 40° C. to about 60° C.
 7. The integratedprocess of claim 1 wherein the organic solvent is removed viadistillation, membrane distillation, or in the presence of asemipermeable membrane.
 8. The integrated process of claim 1 wherein thedecomposing of the solution occurs under room temperature and pressureconditions.
 9. The integrated process of claim 1 wherein the secondaqueous solution comprises water, organic solvent, ammonia, and carbondioxide wherein the concentration of ammonia is higher than theconcentration of carbon dioxide.
 10. The integrated process of claim 1further comprising release of gaseous carbon dioxide from said secondaqueous solution.
 11. The integrated process of claim 1 furthercomprising purifying gaseous carbon dioxide by bubbling the carbondioxide through water to remove organic solvent vapor and ammonia. 12.The integrated process of claim 1 further comprising separating thewater soluble organic solvent from said second aqueous solution.
 13. Theintegrated process of claim 12 wherein waste heat is used to separatethe water soluble organic solvent from said second aqueous solution. 14.The integrated process of claim 1 wherein the water soluble organicsolvent is non-azeotropic.
 15. The integrated process of claim 1 whereinthe water soluble organic solvent has a boiling point below that ofwater.
 16. The integrated process of claim 1 wherein the water solubleorganic solvent is selected from acetone, methyl formate, ethanol, andisopropyl alcohol.
 17. The integrated process of claim 1 wherein thewater soluble organic solvent is acetone.